1. Field of the Invention
The present invention relates to a thermal recording device suitable for use in printers, typewriters and word processor printers and, more particularly, to a thermal recording device of the type in which images are recorded on a recording sheet by means of an ink sheet carrying ink.
2. Related Background Art
Broadly, the recording systems adopted in various recording devices such as printers and typewriters are sorted into three types: namely, ink-jet recording system, wire-dot recording system and thermal recording system. The thermal recording system further can be classified into a thermal transfer type recording system in which characters and patterns are printed by an ink transferred from an ink ribbon, and heat-sensitive type system which makes use of a heat-sensitive recording paper. The thermal transfer type method which makes use of an ink ribbon is typically carried out by serial-type system in which a carriage which carries the ink ribbon together with the recording head is moved along the surface of the recording sheet. In operation of printers of thermal transfer serial printing device, the thermal head is pressed onto the recording paper through the intermediary of the ink ribbon and then the carriage is accelerated. The thermal transfer recording operation is effected only after the carriage is accelerated to a predetermined constant speed. The deceleration of the carriage is commenced after the recording is finished and the thermal head is moved away from the recording sheet after the carriage is stopped.
This known recording system is disadvantageous in that the ink ribbon is consumed wastefully because the ink ribbon is taken-up as a result of the movement of the carriage during acceleration and deceleration in which no recording is conducted. This problem is serious particularly in the case of printers adapted to print data in the form of discrete characters such as electronic typewriters. Namely, in such recording apparatus, the consumption of the ink ribbon per character is so large that the rate of utilization of the ink ribbon is significantly reduced resulting in an extremely uneconomical use of the ink ribbon.
More specifically, in the thermal transfer recording device of the serial recording type, the recording head is pressed onto a platen through the intermediary of the ink ribbon and the recording sheet, while the velocity of the carriage is still zero. This operation will be referred to as "head down" operation, hereinunder. After the head down operation, the carriage is accelerated and the recording, e.g., typing, is commenced after a predetermined constant speed is reached. Then, when the recording is finished, deceleration of the carriage is commenced and, when the the velocity is reduced to zero, the recording head is moved apart from the platen so as to be set at the retracted position. This movement of the head way from the platen will be referred to as "head up operation", hereinafter. When the head is in the down state, the ink ribbon is driven and taken up in synchronization with the movement of the carriage.
Since the head down and head up operations are conducted when the velocity of the carriage is zero, any risk for the portions of the recording sheet other than the recording portions to be contaminated is avoided.
In this recording operation, the ink ribbon is driven and taken up even during acceleration and deceleration of the carriage, though recording is not conducted actually in these periods, resulting in a wasteful use of the ink ribbon.
Under this circumstance, the present applicant has proposed an improved thermal transfer printer in the specification of Japanese Patent Application No. 166632/1981 filed on Oct. 19, 1981 and now laid-open as Japanese Patent Laid-Open No. 67494/1983 since Apr. 22, 1983. Briefly, this improved thermal transfer printer is of the type in which printing is effected by a thermal head carried by a carriage while an ink ribbon is driven, comprising reversing means for reversing the ink ribbon before the start of the printing by an amount which is at least part of the amount taken-up during the movement of the carriage to the printing position. In this improved thermal transfer printer, at least a part of the amount of the ink ribbon which has been taken-up during movement of the carriage to the printing position is reversed, thus attaining an economical use of the ink ribbon.
The present invention proposes a recording device of the type mentioned above, wherein the amount of ink ribbon wastefully used is further reduced.